The present invention relates to color filter arrays for solid-state image devices or liquid crystal display devices, and to a method for producing the same.
As a color filter array formed on a device such as a solid-state image device or a liquid crystal display device, there has been known a color filter array (2) constituted of a yellow filter layer (Y), a magenta filter layer (M), and a cyan filter layer (C) formed so as to be adjoining to each other in the same plane of a substrate (1) (FIG. 1). In the color filter array (2), the filter layers (Y), (M), (C) are arranged in a striped pattern (FIG. 2) or a lattice-like pattern (mosaic) (FIG. 3).
A variety of processes for producing such color filter arrays have been proposed. Among them, a so-called “color resist method” is in wide practical use. In the color resist method, the patterning is effected by exposing a photosensitive resin composition comprising colorants to light and developing, and the patterning is repeated in sequence in the required times.
As the photosensitive resin composition which is employed in the color resist method, those employing pigments as colorants are in wide use. However, such pigments are not suitable for the formation of fine or minute patterns, for they are granular and do not dissolve in developers, and developing residue is generated.
As a photosensitive resin composition for obtaining a finely patterned color filter array, a photosensitive resin composition employing dyes as colorants has also been known. For example, Japanese Patent Application Laid-Open No. 6-75375 discloses a negative photosensitive resin composition comprising dyes, and Japanese Patent Publication No. 7-111485 discloses a positive photosensitive resin composition comprising 10 to 50%, on a dry weight basis, of a dye soluble in the solvent used in the positive photosensitive resin composition. (Hereinafter, “JP-A-” is used for indicating Japanese Patent Application Laid-Open, and “JP-B-” is used for indicating Japanese Patent Publication.)
Colorants comprised in photosensitive resin compositions used for producing color filter arrays, such as those described above, are required to have the following two properties.
(1) Good transmittance property to the exposure light, that is, having high transmittance to the exposure light used for forming the pattern and capable of forming a pattern with a short time exposure.
(2) Good light fastness, that is, no burn-in due to the decolorization of dyes under normal operating conditions
However, none of the dyes employed in conventional photosensitive resin compositions has both of the above-described two properties.
For example, as a dye to be incorporated in a yellow film layer, a pirazolone azo dye (C.I. Solvent Yellow 88) is described in Japanese Patent Publication No. 7-111485. (Hereinafter, “JP-A-” is used for indicating Japanese Patent Application Laid-Open, and “JP-B-” is used for indicating Japanese Patent Publication.) However, this dye exhibits high absorption of visible ray and near ultra violet ray, such as i-line and g-line, and use of this dye makes the exposure time longer. According to JP-B-7-111485, the exposure time is 20 second to form a yellow filter layer using the dye.
A colorant exhibiting a small absorption of visible ray and near ultra violet ray. However, generally colorants exhibiting a small absorption of visible ray and near ultra violet ray is not satisfactory in light fastness. Further, such a dye has low solubility in a photosensitive resin composition, and a photosensitive resin composition containing the dye at a high concentration cannot be easily obtained.
Therefore, it has been difficult to manufacture a color filter array having a practical yellow filter layer.
The inventors of the present invention have made intensive and extensive studies to develop a color filter array having a yellow filter layer having good transmittance property, which enables to form the layer in a short time, as well as good light fastness. As a result, they have found that the use of a specific dye enables the formation of a yellow filter layer satisfactory in light fastness with a short exposure time. The present invention was accomplished based on this finding.